1. Field of the Invention
This invention relates to overrunning coupling assemblies especially for use in vehicular automatic transmissions.
2. Background Art
A typical one-way clutch consists of an inner ring, an outer ring and a locking device between the two rings. The one-way clutch is designed to lock in one direction and to allow free rotation in the other direction. Two types of one-way clutches often used in vehicular, automatic transmissions include:                Roller type which consists of spring loaded rollers between the inner and outer race of the one-way clutch. (Roller type is also used without springs on some applications); and        Sprag type which consists of asymmetrically shaped wedges located between the inner and outer race of the one-way clutch.        
The one-way clutches are typically used in the transmission to prevent an interruption of drive torque (i.e., power flow) during certain gear shifts and to allow engine braking during coasting.
U.S. Pat. No. 5,927,455 discloses a bi-directional overrunning pawl-type clutch having a driving member mounted for power rotation, a driven member mounted for rotation adjacent the driving member, with each of the driving and driven members having pawl engaging shoulders, and a plurality of rigid pawls interposed between the driving and driven members. A control element is mounted for shifting movement between the driving and driven members to control the position of the pawls which are yieldably biased toward positions of engagement extending between the driving and driven members to produce driving engagement therebetween. The control element is shiftable to various positions to permit driving and overrunning in one direction or driving and overrunning in the opposite direction dependent upon the direction of rotation of the driving member.
U.S. Pat. No. 6,244,965 discloses a planar overrunning coupling for transfer of torque from a driving member to a driven member in one direction and which permits freewheeling motion between the members upon a torque reversal. The coupling includes coupling plates situated in close proximity with a strut retainer plate disposed between them, one plate being connected to the driving member and the other plate being connected to the driven member, each plate having strut recesses, a series of struts located in the recesses of one plate so that each strut may be pivoted, thereby allowing the struts to engage the companion recesses in the other coupling plate. The retainer has angularly spaced apertures that register with the struts to permit pivotal movement of the struts when the retainer plate is in one rotary position. The retainer plate, when it is in a second rotary position, prevents pivotal motion of the struts, thereby permitting freewheeling relative motion of the coupling plates.
U.S. Pat. No. 6,290,044 discloses a selectable one-way clutch assembly for use in an automatic transmission comprising a strut plate rotatable about a central hub and having pockets and struts mounted therein for pivotable rotation. A selecting plate concentrically located about an activator hub has teeth extending axially inboard and configured to fit in the apertures in an activator plate. A turning device is selectively operable to activate one-way clutching mode by rotating the pin of a control plate to disengage selecting cams and displace selecting plate teeth inboard beyond the inboard face of the activator plate wherein the struts catch the teeth when the strut plate assembly is rotated in a clutching direction. The catching ends of the struts are cammed in the pockets by ramped camming ends of the teeth when the strut plate assembly is rotated in the opposing direction, thereby allowing freewheeling of the strut plate in the overrun direction.
U.S. Pat. No. 7,258,214 discloses an overrunning coupling assembly and a method of controlling the engagement of planar first and second members wherein two sets of opposed engaging struts are applied with one motion of a single control plate or member. The planar first and second members have inside surfaces extending generally normal to a first axis. The assembly includes free-floating, forward keys and free-floating, reverse keys opposed to the forward keys. The forward and reverse keys are movable between a notch-engaging, engaged position and a disengaged position in which the second member is permitted to free-wheel relative to the first member. The planar control member is disposed between the first and second surfaces and is controllably rotatable about the first axis between first and second angular positions relative to the first member.
U.S. Pat. No. 7,344,010 discloses an overrunning coupling assembly and a method of controlling the engagement of planar first and second members wherein the assembly includes clustered pawls and their respective pawl-holding portions. The planar first and second members have inside surfaces extending generally normal to a first axis. The pawls include a forward set of free-floating pawls and a reverse set of free-floating, clustered pawls. The forward and reverse sets of pawls are movable between a notch-engaging, engaged position and a disengaged position. Because of the clustering, a control element, disposed between the first and second surfaces, need not be fully circular and is controllably rotatable about the first axis between first and second angular positions relative to the first member.
Published patent application US 2006/0278487 discloses an overrunning radial coupling assembly or clutch and a method of controlling the engagement of inner and outer plates or members of the assembly wherein adjacent engaging radial locking pawls are selectively controlled by a single, rotatable control plate or element to obtain full lock, one-way lock and one-way overrun conditions. The assembly includes free-floating, forward pawls and free-floating, reverse pawls adjacent to their respective forward pawls. The forward and reverse pawls are movable between a notch-engaging, engaged position (i.e., full lock condition) and a disengaged position in which the outer member is permitted to free-wheel relative to the inner member in the one-way overrun condition in one direction about a first axis and the outer member is locked to the inner member in the one-way lock condition in the opposite direction. A number of different embodiments of the assembly and method are provided.
Other related U.S. patent publications include U.S. 2005/0279602 and the following U.S. patents:    U.S. Pat. Nos. 7,296,668; 6,854,577; RE 38,498; 6,571,926; 6,505,721; 6,481,551; 6,386,349; 6,333,112; 6,193,038; 6,186,299; 6,129,190; 6,125,980, 6,116,394; 6,065,576; 5,964,331; 5,918,715; and 5,871,071.
One problem associated with the prior art selectable or controllable one-way clutches, is that a control plate or element is used to contain or control both forward and reverse struts in a stationary pocket plate. Consequently, a relatively large quantity of lubricating fluid or oil is required to dampen the forward struts during overrun.
For purposes of this application, the term “coupling” should be interpreted to include clutches or brakes wherein one of the plates is drivably connected to a torque delivery element of a transmission and the other plate is drivably connected to another torque delivery element or is anchored and held stationary with respect to a transmission housing. The terms “coupling,” “clutch” and “brake” may be used interchangeably.